The following U.S. Patents are incorporated herein by reference.
U.S. Pat. No. 4,940,434 discloses a marine propulsion device wherein a pair of generally telescoped bellows surround the universal joint and provide an exhaust passage therebetween which communicates between the inboard engine and the stern drive unit. In the embodiment disclosed herein, the inner bellows rotates with the universal joint while the outer bellows is stationary. The bellows are preferably of helical or spiral configuration and the rotating inner bellows forms an exhaust pump. In one embodiment, the bellows are concentrically disposed, while in another embodiment the bellows are eccentrically mounted.
U.S. Pat. No. 4,773,215 discloses a stern drive marine propulsion system having an inboard engine with an exhaust, an outboard drive unit operatively coupled to the engine and separated therefrom by a transom having two exhaust passages therethrough, and an exhaust control assembly aft of the engine exhaust and forward of the transom and within the boat. The assembly has an inlet connected to the engine exhaust, and has first and second outlets communicating with the respective exhaust passages extending aft through the transom. A valve in the assembly selectively controls communication of the inlet with the first outlet.
U.S. Pat. No. 4,178,873 discloses a marine stern drive including an inboard engine having an exhaust passageway connected to an outboard drive unit having an exhaust passageway. A transom bracket assembly positioned between the engine and the drive unit permits vertical pivoting of the drive unit for steering and horizontal pivoting of the drive unit for steering and horizontal pivoting of the drive unit for trimming. A first exhaust pipe is connected to the inboard engine and a second exhaust pipe is connected to the drive unit. The first exhaust pipe extends outward through the transom of the boat and has an open end position centered on and adjacent the vertical pivot axis and below the vertical pivot axis. The second exhaust pipe extends towards and ends in alignment with the end position of the first exhaust pipe to form an interface which includes an opening between the pipe ends.
U.S. Pat. No. 5,352,141 discloses a marine drive having a spool positioned in the lower horizontal bore and supporting a dual propeller shaft assembly. An exhaust passage includes a passage in the drive housing communicating with the horizontal bore at the spool, and a spool exhaust passage passing exhaust rearwardly through the spool to the propeller through-hub exhaust passages, providing through-hub exhaust through dual propellers. An oil passage in the housing communicates with the horizontal bore forwardly of the exhaust passage and lubricates the dual propeller shaft assembly.
U.S. Pat. No. 5,376,034 discloses a surfacing marine drive having a drive housing with a fore exhaust passage forward of the vertical bore housing the driveshaft, right and left exhaust passages extending rearwardly from the fore exhaust passage on opposite right and left sides of the vertical bore, and an aft exhaust passage extending rearwardly from the right and left exhaust passages and aft of the vertical bore and discharging exhaust into dual counter-rotating surface operating propellers.
U.S. Pat. No. 6,299,496 discloses an exhaust control system for a marine propulsion system used on a marine vessel. Several parameters are monitored by a controller and a controller uses the information provided by these sensors to control the position of a valve within an exhaust conduit assembly. Sound level is measured at a preselected position on the marine vessel and the degree of opening of a valve is controlled to limit the noise level emanating from the exhaust system. Some exhaust can be diverted directly to the atmosphere through the transom as long as the noise level does not exceed a preselected limit, which can typically be a state law regulation. If a noise level is exceeded, the controller forces the exhaust through an underwater discharge point, typically through the propeller hub of the marine propulsion system.
U.S. Pat. No. 7,354,324 discloses a marine propulsion system configured to be preassembled prior to the attachment of a marine engine to the marine vessel. In other words, the marine engine is attached to a transom plate, a gimbal ring, and a bell housing prior to insertion of the engine into the marine vessel. The subassembly is then moved rearwardly to cause the bell housing, gimbal ring, and portion of the transom, bracket to pass through a preformed opening in the transom. Subsequently, a transom ring is attached to the transom bracket to affix the subassembly to the transom. Then a marine drive unit is attached to the bell housing.
U.S. Pat. No. 7,018,255 discloses a marine propulsion system provided with inner and outer bellows, or tubes, which are rigidly attached to both the transom bracket and the driveshaft housing of the sterndrive system. Neither the inner nor outer tubes rotate with the driveshaft. Both the inner and outer tubes, or bellows, allow the driveshaft to rotate relative to the transom bracket about either a steering axis or trim axis. An exhaust passage is defined between the outer surface of the inner tube and the inner surface of the outer tube. This structure provides an efficient positioning of the two tubes while protecting the universal joint within the inner tube from the exhaust gases. Encompassing the inner tube within the outer tube increases the possible area that can be used for the exhaust passage in comparison to providing two individual tubes, one for the universal joint and the other as an exhaust passage.